Arrangement for producing screened printing forms, such as printing cylinders, by means of an electron beam

ABSTRACT

An engraving apparatus for producing a printing matrix such as a printing cylinder including an electron beam producing device having a vacuum chamber opened at its end facing the cylinder and forming a gap with it, the device is adapted to more over the cylinder surface to perform the engraving operation, an end member attached to both ends of the cylinder to assure that the vacuum is not lost by the beam producing device when the engraving is performed at both ends of the cylinder, the end members forming a surface continuity with the cylinder and are removable after the engraving has been performed.

United States Patent [191 Wellendorf et al.

[ June 11, 1974 Dr. Ing. Rudolf Hell GmbH, Kiel, Germany Filed: Feb. 13,1973 App]. No.: 332,129

Assignee:

[30] Foreign Application Priority Data Feb. 15, 1972 Germany 2207090U.S. Cl. 219/121 EB Int. Cl B23k 15/00 Field of Search 219/121 BB, 121EM;

Primary ExaminerJ. V. Truhe Assistant Examiner-G. R. Peterson Attorney,Agent, or FirmErnest F. Marmorek [5 7 ABSTRACT An engraving apparatusfor producing a printing matrix such as a printing cy1inder including anelectron beam producing device having a vacuum chamber opened at its endfacing the cylinder and forming a gap with it, the device is adapted tomore over the cylinder surface to perform the engraving operation, anend member attached to both ends of the cylinder to assure that thevacuum is not lost by the beam producing device when the engraving isperformed at both ends of the cylinder, the end members forming asurface continuity with the cylinder and are removable after theengraving has been performed.

8 Claims, 2 Drawing Figures 1 ARRANGEMENT FOR PRODUCING SCREENEDPRINTING FORMS, SUCH AS PRINTING CYLINDERS, BY MEANS OF AN ELECTRON BEAMCROSS-REFERENCE TO RELATED APPLICATION Reference is had to ourco-pending application, Ser. No. 332,128 filed Feb. 13, 1973.

FIELD OF THE INVENTION The present invention relates to an arrangementfor producing screened printing matrices, especially printing cylinders,by means of an electron beam in which the system producing the electronbeam is placed in a vacuum chamber which is open in the direction of theupper surface of the printing matrix and, which forms an air gap withthe upper surface of the printing matrix and the device with the vacuumchamber and/or the printing matrix are arranged to produce a relativemovement between the vacuum chamber and the printing matrix whileretaining the gap therebetween.

BACKGROUND OF THE INVENTION In the printing industry it has already beenknown in producing screened printing matrices from the upper surface ofa printing form which originally was unprocessed by using a raster sothat cup-shaped recesses are engraved into the upper surface of theprinting cylinder following the printing raster and, in which the depthor the volume of the cup-shaped engravings in the upper surface of theprinting cylinder were given dimensions which represent the tone valuewhich is to printed thereby. During the engraving the depth, that is,the volume of the cup-shaped engravings is controlled by the densityvalues obtained through the electronoptical scanning of an originalpicture set or form which is to be reproduced, such as explained in theApplication of Hans Keller et al, Ser. No. 124,864, filed Mar. 16, 1971entitled Method For Electro-Optical Reproduction of Half-Tone Picturesand assigned to the same assignee as the present application.

For the production of the cup-shaped engravings there are severalmethods known according to which by means of the electronic control ofthe engraving instrument an appropriate quantity of material is removedfrom the upper surface of the printing matrix or cylinder. This can beperformed by means of a cutting tool, such as a diamond stylus, thedepth of penetration of which into the upper surface of the printingform or cylinder is controlled. Such method operates very cleanly. Ithas, however, its disadvantage in that the engraving speed due to themechanical process of the engraving cannot meet the ever increasingrequirements as to speed, in the graphic art industry.

Another method became known according to which the cup-shaped engravingsare produced on the printing cylinder by means of an exactly focused andcontrolled laser beam. Such method is not practical with the presentlyavailable techniques and, at the same time, it produces anunsatisfactory printing quality.

According to a recent discovery, a method is used which employs anelectronic beam, as the engraving means, with which one is able toproduce the necessary cup-shaped engravings reliably and, with a desiredspeed. This method and the associated apparatus for practicing themethod generally resides in that for the processing of an objectaccording to a desired reproduction plan, by means of a charge carryingbeam the picture is recorded. More particularly, the picture is recordedby means of a TV camera and during the recording the deflecting signalsused for controlling the scanning beam of the TV camera tube are usedsimultaneously for the synchronized deflection of the charge carryingbeam which is processing the object to be reproduced. At the same timethe video-signals delivered from the TV camera are used to control theintensity of the charge carrying beam falling on the object underprocessing. With the help of such method satisfactory CUP-shapedengravings can be made, however, one cannot attain a desirable engravingspeed notwithstanding the fact that the electronic beam can be veryquickly deflected within a vacuum chamber into which the workpiece isalso placed. It has been found that only very few cup-shaped engravingscan be made, since in the apparatus proposed by such method theadvancing of the printing matrix or cylinder is slow. Probably a speedcould be attained with such method if the vacuum chamber would bedimensioned so large that the printing matrix could be passed within thevacuum chamber with a desired speed in front of the system producing theelectron beam. This would, however, require an enormous out-layrespecting the size of the vacuum chamber, since the printing cylinderhas a length of several meters and also a large diameter. Also themounting and removal of the printing cylinder into and out of the vacuumchamber would require long idle machine times, to which the timerequired for the evacuation of the chamber is still to be added.

Also a further engraving system has been proposed in which the electronbeam producing system is placed within a bell-shaped vacuum chamberwhich is open in the direction facing the upper surface of the printingcylinder and, which forms a gap with the upper surface of the printingcylinder. However, such a proposed arrangement, is not adapted toperform engraving operations up to the edge regions of the printingcylinder, that is, all the way to the edge at which the cylinder surfaceand the end sides of the cylinder meet, since a loss of the vacuum wouldtake place at that region. As a result, a very considerable part of theupper surface of the cylinder remains unused. In addition, such a methodwould require an unnecessary widening of the printing machine and alsowould cause an increase of the cost of the engraving apparatus itself.

SUMMARY OF THE INVENTION It is, therefore, an object of the presentinvention to provide an improved engraving system for producing ascreened printing matrix by means of an electron beam, which systemeliminates the above described shortcomings of known methods and systemsand, in which the printing matrix can undergo the engraving processwithout being built into a vacuum chamber. In which also the engravingwith an electron beam can be performed all the way to the edge portionsof the printing matrix or cylinder.

According to the present invention, a member is attached at the edgeportions of the printing matrix or cylinder which extends thecylindrical surface of the printing matrix or cylinder under theengraving process.

As a result, by using the engraving system according to the presentinvention, the electron beam of which is located in the center portionof a bell-shaped vacuum system, one may perform the engraving operationall the way to the edge portions of the printing matrix or cylinderwithout the danger of loosing the vacuum of the beam producing device.

It is a preferred feature of the present invention that the memberattached to the printing matrix or cylinder is dimensioned to follow thecurvature of the surface of the printing matrix or cylinder.

Preferably, the member which is attached to the printing matrix is inthe shape of a ring which is coupled gas-tight with each end of theprinting matrix or cylinder or it is arranged fixedly on the frontalsurface of the printing matrix or cylinder by enclosing a gap therewith.

The invention also provides that the member which is attached to theprinting cylinder contains at least one, butpreferably a plurality ofpassages therein for removing the air from between the printing cylinderand the member of attachment.

DESCRIPTION OF THE DRAWINGS The present invention will become morereadily apparent from the following description of preferred embodimentsthereof shown in the accompanying drawings, in which:

FIG. 1 is a schematic representation, partially in section, of thestructural arrangement of the engraving system according to the presentinvention;

FIG. 2 is a partial sectional view of a broken away portion of theprinting form or cylinder illustrating one form of the coupling of theattachment member thereto.

DESCRIPTION OF THE PREFERRED EMBODIMENTS With reference to FIG. 1, anelectron-beam engraving system 11 is illustrated in two differentpositions I and II with respect to a printing cylinder 6 which is underthe process of being engraved and, which is supported in a machine stand12 on an axle 13 for rotation and is driven by a fine drive system notshown in the drawing to avoid a crowding of the drawing with matterswhich do not form part of the present invention. In order that theengraving system 11 which, as illustrated in its position I, iscompletely sitting over the surface of thecylinder 6, could perform theengraving operation up to the edge 14 of the cylinder 6 withoutexperiencing the loss of the vacuum in it, according to the presentinvention a ring-shaped member 15 is attached to both ends thereof,which represents at each end a continuity or extension of thecylindrical surface of the cylinder 6. Such a member 15, as it can beseen in FIG. 1, is secured by means of bolts or other convenientsecuring means to the front or end surfaces of the printing cylinder 6in a gas-tight manner and, rotates with the cylinder 6 itself. Afterfinishing the engraving operation, it is disengaged and removed so thatthe printing cylinder 6 will assume its original and normal length usedin the printing process.

With respect to the details of a preferred construction of the engravingsystem 11 reference should be had to our copending patent applicationSer. No.

332,128, filed Feb. I3, 1973.

With reference to FIG. 2 illustrating another embodiment of theattachment members 15, it is seen that such members 15 are each in theform ofa member fixedly mounted to stand 12 within the engravingapparatus and, which also serves to extend the cylindrical surface ofthe printing cylinder 6 during the engraving process. Te member 15' onits frontal surface with which it faces the printing cylinder 6, isprovided with a plurality of recesses 16 on its upper surface which areprovided in a symmetrical fashion and concentrically with respect to theaxle of the rotation 13. Te recesses 16 matingly face correspondingrecesses and protrusions 17 made in the printing cylinder 6. Themounting of the printing cylinder 6 and the attachment member 15' issuch that a gap is formed between the printing cylinder 6 and themembers 15 and, which is evacuated through a passage 18 by means of avacuum pump coupled thereto and which is not shown to avoid crowding ofthe drawing. As a result, there is formed a constant gap line whichextends over to the surface of the cylinder 6 over its edge portionsand, the vacuum is retained within the engraving system 11 even when theengraving system 11 is in its shown position in FIG. 2 which isidentified by II in FIG. 1.

It should be noted that at both edges or front surfaces of the printingcylinder 6 such attachments 15, 15' are provided, respectively, in eachembodiment. The gap line between the stationary members 15 and thecylinder 6 can take other forms than the illustrated Zig-Zag form. Itcan be a simple straight gap, which makes the machining of the endplates of the printing cylinder 6 much simpler. When several suctionpipes 18 are provided at different radii of the cylinder 6, than theadvantage is attained that by performing the removing of the air fromthe gap at steps, one may obtain a graduated vacuum.

I wish it to be understood that I do not desire to be limited to theexact details of construction shown and described, for obviousmodifications will occur to a person skilled in the art.

Having thus described the invention, what I claim as new and desire tobe secured by Letters Patent, is as follows:

1. An apparatus for producing screened printing matrices on a printingmatrix, comprising, in combination:

Engraving means including a vacuum chamber hav ing a reduced pressureand having an opening defined therein in the part thereof in thedirection of the upper surface of the printing matrix and electron beammeans for producing an electron beam for performing the engravingoperation on the printing matrix, said electron beam means being locatedwithin said vacuum chamber, said electron beam being directed towardsthe opening of said vacuum chamber, said engraving means and saidprinting matrix defining a gap therebetween with the upper surface ofthe printing matrix forming a partial closure of the opening in saidvacuum chamber, moving means for causing a relative movement betweensaid printing matrix and said engraving means while retaining said gaptherebetween, said printing matrix having two opposite end edgeportions, and two end members removably attached to each of saidrespective end edge portions to serve as an extension of the uppersurface of said printing matrix during the engraving process whereby theengraving operation on the printing matrix can be performed to each ofsaid end edge portions while maintaining said partial closure of theopening in said vacuum chamber.

2. The apparatus as claimed in claim 1 wherein each of said end membersis a ring-shaped member coupled 5. The apparatus as claimed in claim 3,wherein said gap is straight and elongated and has dimensions forretaining the vacuum during the engraving process between said engravingmeans, said printing cylinder, and said members.

6. The apparatus as claimed in claim 3, wherein said gap has a Zig-Zagform and has dimensions for retaining the vacuum during the engravingprocess between said engraving means, said printing cylinder and saidmembers.

7. The apparatus as claimed in claim 3, wherein said printing matrix isa printing cylinder, and said moving means comprises means for mountingsaid printing cylinder for rotation about an axle and means for movingsaid engraving means over the surface of said cylinder, said end membersbeing fixedly mounted against rotation with respect to said printingcylinder.

8. The apparatus as claimed in claim 1, wherein said printing matrix isa printing cylinder mounted for rotation about an axle, and said movingmeans comprises means for laterally moving said engraving means over theupper surface of said printing cylinder from one of said edge portionsto the other of said edge portions, said end members being fixedlymounted for rotation with said printing cylinder.

1. An apparatus for producing screened printing matrices on a printingmatrix, comprising, in combination: 1 engraving means including a vacuumchamber having a reduced pressure and having an opening defined thereinin the part thereof in the direction of the upper surface of theprinting matrix and electron beam means for producing an electron beamfor performing the engraving operation on the printing matrix, saidelectron beam means being located within said vacuum chamber, saidelectron beam being directed towards the opening of said vacuum chamber,said engraving means and said printing matrix defining a gaptherebetween with the upper surface of the printing matrix forming apartial closure of the opening in said vacuum chamber, moving means forcausing a relative movement between said printing matrix and saidengraving means while retaining said gap therebetween, said printingmatrix having two opposite end edge portions, and two end membersremovably attached to each of said respective end edge portions to serveas an extension of the upper surface of said printing matrix during theengraving process whereby the engraving operation on the printing matrixcan be performed to each of said end edge portions while maintainingsaid partial closure of the opening in said vacuum chamber.
 2. Theapparatus as claimed in claim 1 wherein each of said end members is aring-shaped member coupled to each said end edge portions of saidprinting matrix in gas-tight fashion.
 3. The apparatus as claimed inclaim 1, wherein means are provided for coupling said end members tosaid respective end edge portions of said printing matrix andmaintaining the gap between said printing matrix and each of said endmembers.
 4. The apparatus as claimed in claim 3, wherein each of saidmember has provided therein at least one passage for removing the airfrom the gap between the engraving means, the printing matrix and saidmembers.
 5. The apparatus as claimed in claim 3, wherein said gap isstraight and elongated and has dimensions for retaining the vacuumduring the engraving process between said engraving means, said printingcylinder, and said members.
 6. The apparatus as claimed in claim 3,wherein said gap has a Zig-Zag form and has dimensions for retaining thevacuum during the engraving process between said engraving means, saidprinting cylinder and said members.
 7. The apparatus as claimed in claim3, wherein said printing matrix is a printing cylinder, and said movingmeans comprises means for mounting said printing cylinder for rotationabout an axle and means for moving said engraving means over the surfaceof said cylinder, said end members being fixedly mounted againstrotation with respect to said printing cylinder.
 8. The apparatus asclaimed in claim 1, wherein said printing matrix is a printing cylindermounted for rotation about an axle, and said moving means comprisesmeans for laterally moving said engraving means over the upper surfaceof said printing cylinder from one of saId edge portions to the other ofsaid edge portions, said end members being fixedly mounted for rotationwith said printing cylinder.